$ perl -le'no strict;      print $INC{ "strict.pm" } ?1:0'
1   # False positive

$ perl -le'{ use strict; } print $INC{ "strict.pm" } ?1:0'
1   # False positive

$ perl -le'use JSON;       print $INC{ "strict.pm" } ?1:0'
1   # False positive

$ perl -le'use v5.20;      print $INC{ "strict.pm" } ?1:0'
0   # False negative